The present invention relates to a hammer drill. More particularly, this invention concerns a chuck and a tool for a hammer drill.
Chucks and tools for hammer drills have been proposed in the art, wherein a tool has a shank receivable axially in a receptacle of a chuck. The shank has a radially outwardly open recess which is closed at its both axial ends and adapted to receive a tool-holding element such as a ball. The shank also has axially extending groove separate from the recess and open at a free end of the shank, which groove is adapted to receive elongated projection formed in an inner wall of the receptacle of the chuck. The thus-constructed shank of the tool and the chuck transmit both a torque and an axial impact from the hammer drill to the tool.
Shanks of the known tools have been of a substantially cylindrical shape, and for this reason possessed certain disadvantages. The tools with the cylindrical shanks cannot be directly mounted in the type of chuck having conical receptacles which, although now old-fashioned, is still widely used in industry. In order to mount the tool with the cylindrical shank in a chuck having a conical receptacle, additional adapters must be used, which make the process of mounting difficult and complicated.
Furthermore, although it is generally desirable that in the case of the cylindrical shank impact energy is transmitted with great efficiency, there are instances when a reduction in the impact-energy transmission in operation of a hammer drill is preferred. Particularly, when a hammer drill having a great impact energy is used for driving small tools, e.g. drill bits, it is desirable to provide a comparatively small efficiency of energy transmission.